Negative symptoms are core symptoms of schizophrenia associated with poorer clinical outcome (Strauss et al., 2010). They can be clinically subdivided into primary and secondary features, representing different phenomenology and pathophysiological mechanisms (Miller et al., 1994). Secondary negative symptoms phenotypically present as primary symptoms, but are attributed to external causes. Positive symptom severity, depression and antipsychotic side-effects are known sources of secondary negative symptoms (Carpenter et al., 1985). Discriminating whether a negative symptom is primary or secondary is clinically relevant as it might require specific, and often opposite interventions (Miller et al., 1994). Despite the development of new symptom severity rating scales, none have considered this distinction.